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1.
Nature ; 578(7795): 392-396, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-32025037

RESUMEN

Extensive efforts have been made to harvest energy from water in the form of raindrops1-6, river and ocean waves7,8, tides9 and others10-17. However, achieving a high density of electrical power generation is challenging. Traditional hydraulic power generation mainly uses electromagnetic generators that are heavy, bulky, and become inefficient with low water supply. An alternative, the water-droplet/solid-based triboelectric nanogenerator, has so far generated peak power densities of less than one watt per square metre, owing to the limitations imposed by interfacial effects-as seen in characterizations of the charge generation and transfer that occur at solid-liquid1-4 or liquid-liquid5,18 interfaces. Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminium electrode. We show that spreading of an impinged water droplet on the device bridges the originally disconnected components into a closed-loop electrical system, transforming the conventional interfacial effect into a bulk effect, and so enhancing the instantaneous power density by several orders of magnitude over equivalent devices that are limited by interfacial effects.

2.
Am J Epidemiol ; 2024 May 20.
Artículo en Inglés | MEDLINE | ID: mdl-38770979

RESUMEN

Racial/ethnic disparities in the association between short-term (e.g. days, weeks) ambient fine particulate matter (PM2.5) and temperature exposures and stillbirth in the US have been understudied. A time-stratified, case-crossover design using a distributed lag non-linear model (0 to 6-day lag) estimated stillbirth odds due to short-term increases in average daily PM2.5 and temperature exposures among 118,632 Medicaid recipients from 2000-2014. Disparities by maternal race/ethnicity (Black, White, Hispanic, Asian, American Indian) and zip-code level socioeconomic status (SES) were assessed. In the temperature-adjusted model, a 10 µg/m3 increase in PM2.5 concentration was marginally associated with increased stillbirth odds at lag 1 (0.68% 95%CI:[-0.04,1.40]) and lag 2 (0.52% 95%CI:[-0.03,1.06]), but not lag 0-6 (2.80% 95%CI:[-0.81,6.45]). An association between daily PM2.5 concentrations and stillbirth odds was found among Black individuals at the cumulative lag (0-6 days: 9.26% 95%CI:[3.12,15.77]), but not among other races/ethnicities. A stronger association between PM2.5 concentrations and stillbirth odds existed among Black individuals living in zip codes with the lowest median household income (lag0-6:14.13% 95%CI:[4.64,25.79]). Short-term temperature increases were not associated with stillbirth risk among any race/ethnicity. Black Medicaid enrollees, and especially those living in lower SES areas, may be more vulnerable to stillbirth due to short-term increases in PM2.5 exposure.

3.
Environ Sci Technol ; 58(2): 1097-1108, 2024 Jan 16.
Artículo en Inglés | MEDLINE | ID: mdl-38175714

RESUMEN

Associations between gaseous pollutant exposure and stillbirth have focused on exposures averaged over trimesters or gestation. We investigated the association between short-term increases in nitrogen dioxide (NO2) and ozone (O3) concentrations and stillbirth risk among a national sample of 116 788 Medicaid enrollees from 2000 to 2014. A time-stratified case-crossover design was used to estimate distributed (lag 0-lag 6) and cumulative lag effects, which were adjusted for PM2.5 concentration and temperature. Effect modification by race/ethnicity and proximity to hydraulic fracturing (fracking) wells was assessed. Short-term increases in the NO2 and O3 concentrations were not associated with stillbirth in the overall sample. Among American Indian individuals (n = 1694), a 10 ppb increase in NO2 concentrations was associated with increased stillbirth odds at lag 0 (5.66%, 95%CI: [0.57%, 11.01%], p = 0.03) and lag 1 (4.08%, 95%CI: [0.22%, 8.09%], p = 0.04) but not lag 0-6 (7.12%, 95%CI: [-9.83%, 27.27%], p = 0.43). Among participants living in zip codes within 15 km of active fracking wells (n = 9486), a 10 ppb increase in NO2 concentration was associated with increased stillbirth odds in single-day lags (2.42%, 95%CI: [0.37%, 4.52%], p = 0.02 for lag 0 and 1.83%, 95%CI: [0.25%, 3.43%], p = 0.03 for lag 1) but not the cumulative lag (lag 0-6) (4.62%, 95%CI: [-2.75%, 12.55%], p = 0.22). Odds ratios were close to the null in zip codes distant from fracking wells. Future studies should investigate the role of air pollutants emitted from fracking and potential racial disparities in the relationship between short-term increases in NO2 concentrations and stillbirth.


Asunto(s)
Contaminantes Atmosféricos , Contaminación del Aire , Ozono , Embarazo , Femenino , Humanos , Contaminación del Aire/análisis , Estudios Cruzados , Dióxido de Nitrógeno/análisis , Material Particulado/análisis , Mortinato/epidemiología , Contaminantes Atmosféricos/análisis , Ozono/análisis , Exposición a Riesgos Ambientales/análisis
4.
Environ Res ; 242: 117742, 2024 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-38007077

RESUMEN

BACKGROUND: Solar activity has been linked to biological mechanisms important to pregnancy, including folate and melatonin levels and inflammatory markers. Thus, we aimed to investigate the association between gestational solar activity and pregnancy loss. METHODS: Our study included 71,963 singleton births conceived in 2002-2016 and delivered at an academic medical center in Eastern Massachusetts. We studied several solar activity metrics, including sunspot number, Kp index, and ultraviolet radiation, with data from the NASA Goddard Space Flight Center and European Centre for Medium-Range Weather Forecasts. We used a novel time series analytic approach to investigate associations between each metric from conception through 24 weeks of gestation and the number of live birth-identified conceptions (LBICs) -the total number of conceptions in each week that result in a live birth. This approach fits distributed lag models to data on LBICs, adjusted for time trends, and allows us to infer associations between pregnancy exposure and pregnancy loss. RESULTS: Overall, the association between solar activity during pregnancy and pregnancy loss varied by exposure metric. For sunspot number, we found that an interquartile range increase in sunspot number (78·7 sunspots) in all of the first 24 weeks of pregnancy was associated with 14·0 (95% CI: 6·5, 21·3) more pregnancy losses out of the average 92 LBICs in a week, and exposure in weeks ten through thirteen was identified as a critical window. Although not statistically significant, higher exposure to Kp index and to UV radiation across all 24 weeks of pregnancy was associated with more and less pregnancy losses, respectively. CONCLUSION: While exposure to certain metrics of solar activity (i.e., sunspot number) throughout the first 24 weeks of pregnancy may be associated with pregnancy losses, exposure to other metrics were not. Solar activity is a complex phenomenon, and more studies are needed to clarify underlying pathways.


Asunto(s)
Aborto Espontáneo , Nacimiento Vivo , Embarazo , Femenino , Humanos , Actividad Solar , Rayos Ultravioleta , Aborto Espontáneo/epidemiología , Aborto Espontáneo/etiología , Massachusetts/epidemiología
5.
Intern Med J ; 54(4): 613-619, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-37929813

RESUMEN

BACKGROUND: Nocardia is a ubiquitous saprophyte capable of causing human disease. Disease is primarily respiratory or cutaneous, usually acquired via inhalation or inoculation. Under the influence of environmental and host factors, Nocardia incidence and species distribution demonstrate geographical variation. AIMS: To examine for differences in Nocardia incidence within Western Australia (WA) and analyse species distribution in the context of prior published studies. To analyse antibiogram data from a nationwide passive antimicrobial resistance surveillance program. METHODS: Retrospective extraction of laboratory data for Western Australian Nocardia isolates over a 21-year period. Analysis of Nocardia antimicrobial susceptibility testing data submitted to the Australian Passive Antimicrobial Resistance Surveillance (APAS) program between 2005 and 2022. RESULTS: Nine hundred sixty WA isolates were identified, giving an annual incidence of 3.03 per 100 000 population with apparent latitudinal variation. The four most common species identified within WA and amongst APAS isolates were N. nova, N. cyriacigeorgica, N. brasiliensis and N. farcinica. APAS data demonstrated that all species exhibited high rates of susceptibility to linezolid (100%) and trimethoprim-sulfamethoxazole (98%). Amikacin (>90% susceptibility for all species except N. transvalensis) was the next most active parenteral agent, superior to both carbapenems and third-generation cephalosporins. Susceptibility to oral antimicrobials (other than linezolid) demonstrated significant interspecies variation. CONCLUSIONS: We demonstrate geographical variation in the distribution of Nocardia incidence. Four species predominate in the Australian setting, and nationwide data confirm a high in vitro susceptibility to trimethoprim-sulphamethoxazole and linezolid, justifying their ongoing role as part of first-line empiric therapy.

6.
Am J Epidemiol ; 192(4): 644-657, 2023 04 06.
Artículo en Inglés | MEDLINE | ID: mdl-36562713

RESUMEN

Distributed lag models (DLMs) are often used to estimate lagged associations and identify critical exposure windows. In a simulation study of prenatal nitrogen dioxide (NO2) exposure and birth weight, we demonstrate that bias amplification and variance inflation can manifest under certain combinations of DLM estimation approaches and time-trend adjustment methods when using low-spatial-resolution exposures with extended lags. Our simulations showed that when using high-spatial-resolution exposure data, any time-trend adjustment method produced low bias and nominal coverage for the distributed lag estimator. When using either low- or no-spatial-resolution exposures, bias due to time trends was amplified for all adjustment methods. Variance inflation was higher in low- or no-spatial-resolution DLMs when using a long-term spline to adjust for seasonality and long-term trends due to concurvity between a distributed lag function and secular function of time. NO2-birth weight analyses in a Massachusetts-based cohort showed that associations were negative for exposures experienced in gestational weeks 15-30 when using high-spatial-resolution DLMs; however, associations were null and positive for DLMs with low- and no-spatial-resolution exposures, respectively, which is likely due to bias amplification. DLM analyses should jointly consider the spatial resolution of exposure data and the parameterizations of the time trend adjustment and lag constraints.


Asunto(s)
Contaminantes Atmosféricos , Contaminación del Aire , Embarazo , Femenino , Humanos , Contaminantes Atmosféricos/análisis , Material Particulado/análisis , Peso al Nacer , Dióxido de Nitrógeno
7.
Am J Epidemiol ; 192(7): 1105-1115, 2023 07 07.
Artículo en Inglés | MEDLINE | ID: mdl-36963378

RESUMEN

Previous studies have examined the association between prenatal nitrogen dioxide (NO2)-a traffic emissions tracer-and fetal growth based on ultrasound measures. Yet, most have used exposure assessment methods with low temporal resolution, which limits the identification of critical exposure windows given that pregnancy is relatively short. Here, we used NO2 data from an ensemble model linked to residential addresses at birth to fit distributed lag models that estimated the association between NO2 exposure (resolved weekly) and ultrasound biometric parameters in a Massachusetts-based cohort of 9,446 singleton births from 2011-2016. Ultrasound biometric parameters examined included biparietal diameter (BPD), head circumference, femur length, and abdominal circumference. All models adjusted for sociodemographic characteristics, time trends, and temperature. We found that higher NO2 was negatively associated with all ultrasound parameters. The critical window differed depending on the parameter and when it was assessed. For example, for BPD measured after week 31, the critical exposure window appeared to be weeks 15-25; 10-parts-per-billion higher NO2 sustained from conception to the time of measurement was associated with a lower mean z score of -0.11 (95% CI: -0.17, -0.05). Our findings indicate that reducing traffic emissions is one potential avenue to improving fetal and offspring health.


Asunto(s)
Contaminantes Atmosféricos , Contaminación del Aire , Exposición Materna , Femenino , Humanos , Recién Nacido , Embarazo , Contaminantes Atmosféricos/efectos adversos , Contaminantes Atmosféricos/análisis , Contaminación del Aire/efectos adversos , Contaminación del Aire/análisis , Desarrollo Fetal , Massachusetts/epidemiología , Exposición Materna/efectos adversos , Dióxido de Nitrógeno/efectos adversos , Dióxido de Nitrógeno/análisis
8.
Small ; 19(35): e2300441, 2023 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-37118851

RESUMEN

The reaction kinetics of hydrogen evolution reaction (HER) is largely determined by balancing the Volmer step in alkaline media. Bifunctionality as a proposed strategy can divide the work of water dissociation and intermediates (OH* and H*) adsorption/desorption. However, sluggish OH* desorption plagues water re-adsorption, which leads to poisoning effects of active sites. Some active sites may even directly act as spectators and do not participate in the reaction. Furthermore, the activity comparison under approximate nanostructure between bifunctional effect and single-exposed active sites is not fully understood. Here, a facile three-step strategy is adopted to successfully grow molybdenum disulfide (MoS2 ) on cobalt-containing nitrogen-doped carbon nanotubes (Co-NCNTs), forming obvious dual active domains. The active sites on domains of Co-NCNTs and MoS2  and the tuned electronic structure at the heterointerface trigger the bifunctional effect to balance the Volmer step and improve the catalytic activity. The HER driven by the bifunctional effect can significantly optimize the Gibbs free energy of water dissociation and hydrogen adsorption, resulting in fast reaction kinetics and superior catalytic performance. As a result, the Co-NCNTs/MoS2  catalyst outperforms other HER electrocatalysts with low overpotential (58 and 84 mV at 10 mA cm-2  in alkaline and neutral conditions, respectively), exceptional stability, and negligible degradation.

9.
J Urol ; 209(3): 600-610, 2023 03.
Artículo en Inglés | MEDLINE | ID: mdl-36475807

RESUMEN

PURPOSE: Varicocele is a common condition in adolescence and the most common correctable cause of infertility. This study aimed to analyze and compare the outcomes of scrotal antegrade sclerotherapy and laparoscopic Palomo surgery in a tertiary referral center. MATERIALS AND METHODS: Patients with left grade 3 varicocele indicated for surgery were prospectively enrolled and randomly allocated to the scrotal antegrade sclerotherapy and laparoscopic Palomo surgery groups, with their respective contralateral normal testes taken as controls. The primary outcome measures were clinical varicocele recurrence, testicular catch-up growth, and postoperative hydrocele. All patients were evaluated clinically and using Doppler ultrasound by radiologists. RESULTS: From 2015 to 2020, 113 patients completed the study and were statistically analyzed (scrotal antegrade sclerotherapy, n = 57; laparoscopic Palomo surgery, n = 56). All patients had significantly smaller testes preoperatively; the testicular volume differences with control testes were -23% in scrotal antegrade sclerotherapy and -19% in laparoscopic Palomo surgery. At 12-month follow-up, there were no statistically significant differences in clinical recurrences between the 2 groups (scrotal antegrade sclerotherapy = 5.3% vs laparoscopic Palomo surgery = 5.4%, P > .05, noninferiority test). Testicular catch-up growths were observed in both groups; the mean testicular volume difference between the treatment and control testes decreased from -23% to -8.1% in scrotal antegrade sclerotherapy (P < .001) and from -19% to -9.3% in laparoscopic Palomo surgery (P < .001) at 12-month follow-up. There was no postoperative hydrocele in the scrotal antegrade sclerotherapy group compared to 7 cases in the laparoscopic Palomo surgery group (0% vs 13%, P = .006). CONCLUSIONS: Both scrotal antegrade sclerotherapy and laparoscopic Palomo surgery are safe and effective procedures for treatment of adolescent varicocele with significant positive effect on testicular catch-up growth. Scrotal antegrade sclerotherapy is not inferior to laparoscopic Palomo surgery in terms of clinical recurrence rate and has significantly less postoperative hydrocele.


Asunto(s)
Laparoscopía , Varicocele , Masculino , Humanos , Adolescente , Varicocele/cirugía , Escleroterapia/métodos , Estudios Prospectivos , Estudios Retrospectivos , Laparoscopía/métodos
10.
Epidemiology ; 34(5): 673-680, 2023 09 01.
Artículo en Inglés | MEDLINE | ID: mdl-37255239

RESUMEN

BACKGROUND: Misclassification bias is a common concern in epidemiologic studies. Despite strong bias on main effects, gene-environment interactions have been shown to be biased towards the null under gene-environment independence. In the context of a recent article examining the interaction between nerve agent exposure and paraoxonase-1 gene on Gulf War Illness, we aimed to assess the impact of recall bias-a common misclassfication bias-on the identification of gene-environment interactions when the independence assumption is violated. METHODS: We derive equations to quantify the bias of the interaction, and numerically illustrate these results by simulating a case-control study of 1000 cases and 1000 controls. Simulation input parameters included exposure prevalence, strength of gene-environment dependence, strength of the main effect, exposure specificity among cases, and strength of the gene-environment interaction. RESULTS: We show that, even if gene-environment independence is violated, we can bound possible gene-environment interactions by knowing the strength and direction of the gene-environment dependence ( ) and the observed gene-environment interaction ( )-thus often still allowing for the identification of such interactions. Depending on whether is larger or smaller than the inverse of , is a lower (if ) or upper (if ) bound for the true interaction. In addition, the bias magnitude is somewhat predictable by examining other characteristics such as exposure prevalence, the strength of the exposure main effect, and directions of the recall bias and gene-environment dependence. CONCLUSIONS: Even if gene-environment dependence exists, we may still be able to identify gene-environment interactions even when misclassification bias is present.


Asunto(s)
Interacción Gen-Ambiente , Humanos , Estudios de Casos y Controles , Sesgo , Simulación por Computador
11.
Immunity ; 41(5): 830-42, 2014 Nov 20.
Artículo en Inglés | MEDLINE | ID: mdl-25517615

RESUMEN

Spontaneous T cell responses against tumors occur frequently and have prognostic value in patients. The mechanism of innate immune sensing of immunogenic tumors leading to adaptive T cell responses remains undefined, although type I interferons (IFNs) are implicated in this process. We found that spontaneous CD8(+) T cell priming against tumors was defective in mice lacking stimulator of interferon genes complex (STING), but not other innate signaling pathways, suggesting involvement of a cytosolic DNA sensing pathway. In vitro, IFN-? production and dendritic cell activation were triggered by tumor-cell-derived DNA, via cyclic-GMP-AMP synthase (cGAS), STING, and interferon regulatory factor 3 (IRF3). In the tumor microenvironment in vivo, tumor cell DNA was detected within host antigen-presenting cells, which correlated with STING pathway activation and IFN-? production. Our results demonstrate that a major mechanism for innate immune sensing of cancer occurs via the host STING pathway, with major implications for cancer immunotherapy.


Asunto(s)
Linfocitos T CD8-positivos/inmunología , ADN/inmunología , Activación de Linfocitos/inmunología , Melanoma Experimental/inmunología , Proteínas de la Membrana/inmunología , Inmunidad Adaptativa , Proteínas Adaptadoras Transductoras de Señales/genética , Traslado Adoptivo , Animales , Células Presentadoras de Antígenos/citología , Células Presentadoras de Antígenos/inmunología , Línea Celular Tumoral , Proliferación Celular , Células Dendríticas/inmunología , Inmunidad Innata , Factor 3 Regulador del Interferón/genética , Interferón beta/biosíntesis , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Factor 88 de Diferenciación Mieloide/genética , Nucleotidiltransferasas , Receptores de Antígenos de Linfocitos T/inmunología , Receptores Purinérgicos P2X7/genética , Receptor Toll-Like 4/genética , Receptor Toll-Like 9/genética , Microambiente Tumoral/inmunología
12.
Int J Gynecol Pathol ; 42(4): 421-425, 2023 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-36044308
13.
J Am Chem Soc ; 144(37): 17097-17109, 2022 Sep 21.
Artículo en Inglés | MEDLINE | ID: mdl-36066387

RESUMEN

Solar carbon dioxide (CO2) conversion is an emerging solution to meet the challenges of sustainable energy systems and environmental/climate concerns. However, the construction of isolated active sites not only influences catalytic activity but also limits the understanding of the structure-catalyst relationship of CO2 reduction. Herein, we develop a universal synthetic protocol to fabricate different single-atom metal sites (e.g., Fe, Co, Ni, Zn, Cu, Mn, and Ru) anchored on the triazine-based covalent organic framework (SAS/Tr-COF) backbone with the bridging structure of metal-nitrogen-chlorine for high-performance catalytic CO2 reduction. Remarkably, the as-synthesized Fe SAS/Tr-COF as a representative catalyst achieved an impressive CO generation rate as high as 980.3 µmol g-1 h-1 and a selectivity of 96.4%, over approximately 26 times higher than that of the pristine Tr-COF under visible light irradiation. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to the synergic effect of atomically dispersed metal sites and Tr-COF host, decreasing the reaction energy barriers for the formation of *COOH intermediates and promoting CO2 adsorption and activation as well as CO desorption. This work not only affords rational design of state-of-the-art catalysts at the molecular level but also provides in-depth insights for efficient CO2 conversion.

14.
Environ Sci Technol ; 56(23): 16582-16601, 2022 12 06.
Artículo en Inglés | MEDLINE | ID: mdl-36367480

RESUMEN

Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.


Asunto(s)
Contaminación del Aire Interior , Compuestos Orgánicos Volátiles , Contaminación del Aire Interior/análisis , Fotoquímica/métodos , Catálisis , Oxidación-Reducción
15.
Occup Environ Med ; 2022 May 02.
Artículo en Inglés | MEDLINE | ID: mdl-35501127

RESUMEN

OBJECTIVES: Mechanisms underlying the carcinogenicity of night shift work remain uncertain. One compelling yet understudied cancer mechanism may involve altered DNA methylation in circadian genes due to melatonin secretion patterns. The objective of this study was to explore the relationship between melatonin secretion patterns and circadian gene methylation among day and night shift workers. METHODS: Female healthcare employees (n=38 day workers, n=36 night shift workers) for whom we had urinary 6-sulfatoxymelatonin secretion data from a previous study were recontacted. New blood samples were collected and used to measure methylation levels at 1150 CpG loci across 22 circadian genes using the Illumina Infinium MethylationEPIC beadchip. Linear regression was used to examine the association between melatonin (acrophase and mesor) and M values for each CpG site (false discovery rate, q=0.2), while testing for effect modification by shift work status. RESULTS: Among night shift workers, a higher mesor (24 hours of mean production of melatonin) was associated with increased methylation in the body of RORA (q=0.02) and decreased methylation in the putative promoter region of MTNR1A (q=0.03). Later acrophase (ie, time of peak concentration) was associated with increased methylation in the putative promoter region of MTNR1A (q=0.20) and decreased methylation in the body of PER3 (q=0.20). No associations were identified among day workers. CONCLUSIONS: In conclusion, patterns in melatonin secretion were associated with differential circadian gene methylation among night shift workers. Melatonin and alteration of DNA methylation in circadian genes may be one pathway towards increased cancer risk, although larger-scale studies examining multiple time points are needed.

16.
Angew Chem Int Ed Engl ; 60(8): 4192-4198, 2021 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-33197100

RESUMEN

Regulating the local environment and structure of metal center coordinated by nitrogen ligands (M-N4 ) to accelerate overall reaction dynamics of the electrochemical CO2 reduction reaction (CO2 RR) has attracted extensive attention. Herein, we develop an axial traction strategy to optimize the electronic structure of the M-N4 moiety and construct atomically dispersed nickel sites coordinated with four nitrogen atoms and one axial oxygen atom, which are embedded within the carbon matrix (Ni-N4 -O/C). The Ni-N4 -O/C electrocatalyst exhibited excellent CO2 RR performance with a maximum CO Faradic efficiency (FE) close to 100 % at -0.9 V. The CO FE could be maintained above 90 % in a wide range of potential window from -0.5 to -1.1 V. The superior CO2 RR activity is due to the Ni-N4 -O active moiety composed of a Ni-N4 site with an additional oxygen atom that induces an axial traction effect.

17.
J Am Chem Soc ; 142(5): 2404-2412, 2020 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-31902210

RESUMEN

Atomically dispersed transition metal active sites have emerged as one of the most important fields of study because they display promising performance in catalysis and have the potential to serve as ideal models for fundamental understanding. However, both the preparation and determination of such active sites remain a challenge. The structural engineering of carbon- and nitrogen-coordinated metal sites (M-N-C, M = Fe, Co, Ni, Mn, Cu, etc.) via employing new heteroatoms, e.g., P and S, remains challenging. In this study, carbon nanosheets embedded with nitrogen and phosphorus dual-coordinated iron active sites (denoted as Fe-N/P-C) were developed and determined using cutting edge techniques. Both experimental and theoretical results suggested that the N and P dual-coordinated iron sites were favorable for oxygen intermediate adsorption/desorption, resulting in accelerated reaction kinetics and promising catalytic oxygen reduction activity. This work not only provides efficient way to prepare well-defined single-atom active sites to boost catalytic performance but also paves the way to identify the dual-coordinated single metal atom sites.

18.
Small ; 16(28): e2002212, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32510832

RESUMEN

Developing efficient earth-abundant MoS2 based hydrogen evolution reaction (HER) electrocatalysts is important but challenging due to the sluggish kinetics in alkaline media. Herein, a strategy to fabricate a high-performance MoS2 based HER electrocatalyst by modulating interface electronic structure via metal oxides is developed. All the heterostructure catalysts present significant improvement of HER electrocatalytic activities, demonstrating a positive role of metal oxides decoration in promoting the rate-limited water dissociation step for the HER mechanism in alkaline media. The as-obtained MoS2 /Ni2 O3 H catalyst exhibits a low overpotential of 84 mV at 10 mA cm-2 and small charge-transfer resistance of 1.5 Ω in 1 m KOH solution. The current density (217 mA cm-2 ) at the overpotential of 200 mV is about 2 and 24 times higher than that of commercial Pt/C and bare MoS2 , respectively. Additionally, these MoS2 /metal oxides heterostructure catalysts show outstanding long-term stability under a harsh chronopotentiometry test. Theoretical calculations reveal the varied sensitivity of 3d-band in different transition oxides, in which Ni-3d of Ni2 O3 H is evidently activated to achieve fast electron transfer for HER as the electron-depletion center. Both electronic properties and energetic reaction trends confirm the high electroactivity of MoS2 /Ni2 O3 H in the adsorption and dissociation of H2 O for highly efficient HER in alkaline media.

19.
Phys Chem Chem Phys ; 22(7): 4080-4085, 2020 Feb 21.
Artículo en Inglés | MEDLINE | ID: mdl-32031181

RESUMEN

Many organic molecules have unique magnetic properties and can potentially serve as excellent molecular spin devices, which is worth exploring deeply. Here, the spin transport properties of Mn, Fe, Co and Cu porphyrin dimer devices are investigated based on the first principles method. The spin filtering efficiencies of these molecular devices are maintained at 100% within certain applied voltage ranges and magnetoresistance ratios are higher than 108% which increase as the voltage increases. To explain the excellent spin-filtering and giant magnetoresistance effects, analysis of spin electron densities and transmission spectra indicates that magnetic properties are mainly contributed by the metal atoms and their neighbouring N atoms. From the transmission pathway studies, spin electrons come mainly through the π-conjugated structure of the metal porphyrin ring. Interestingly, in the Cu porphyrin dimer device, magnetic moments of the Cu-N structure in the Cu porphyrin dimer device show spin behaviors different from those of Mn, Fe and Co porphyrin dimer devices.

20.
Bioinformatics ; 34(17): 2889-2898, 2018 09 01.
Artículo en Inglés | MEDLINE | ID: mdl-29648582

RESUMEN

Motivation: Processing of transcripts at the 3'-end involves cleavage at a polyadenylation site followed by the addition of a poly(A)-tail. By selecting which site is cleaved, the process of alternative polyadenylation enables genes to produce transcript isoforms with different 3'-ends. To facilitate the identification and treatment of disease-causing mutations that affect polyadenylation and to understand the sequence determinants underlying this regulatory process, a computational model that can accurately predict polyadenylation patterns from genomic features is desirable. Results: Previous works have focused on identifying candidate polyadenylation sites and classifying tissue-specific sites. By training on how multiple sites in genes are competitively selected for polyadenylation from 3'-end sequencing data, we developed a deep learning model that can predict the tissue-specific strength of a polyadenylation site in the 3' untranslated region of the human genome given only its genomic sequence. We demonstrate the model's broad utility on multiple tasks, without any application-specific training. The model can be used to predict which polyadenylation site is more likely to be selected in genes with multiple sites. It can be used to scan the 3' untranslated region to find candidate polyadenylation sites. It can be used to classify the pathogenicity of variants near annotated polyadenylation sites in ClinVar. It can also be used to anticipate the effect of antisense oligonucleotide experiments to redirect polyadenylation. We provide analysis on how different features affect the model's predictive performance and a method to identify sensitive regions of the genome at the single-based resolution that can affect polyadenylation regulation. Supplementary information: Supplementary data are available at Bioinformatics online.


Asunto(s)
Poliadenilación , Regiones no Traducidas 3' , Regulación de la Expresión Génica , Genoma Humano , Genómica , Humanos , Poli A
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